I'm afraid I don't take notes or keep a log. Sometimes I learn the same thing over and over.
I do have a quilter friend that I email almost every day. We both share the problems we're having, and the solution, and we've both commented that we've looked back at past emails when trying to remember something that happened in the past. I'm not recommending that method of keeping track, though - it's harder to find something in emails than it would be in an organized log.